Zoo Atlanta Panda cubs, Mei Lun and Lei Huan, in October 2013.
ATLANTA (CNN) -- They're cute, they're cuddly, but the one thing the twin panda cubs at Zoo Atlanta are not is male.
Mei Lun and Mei Huan were born in July and were originally determined to be boys. Rebecca Snyder, curator of mammals at Zoo Atlanta, told HLN on Monday that zoo officials found out in November that the twin giant pandas are actually girls. "It's possible to make mistakes," Snyder said.
It's very hard to determine the sex of pandas, she said, as there are very few external cues regarding the animals' gender before they turn 3. The zoo relies on their colleagues from China's Chengdu Research Base of Giant Panda Breeding to determine the sex.
"In the past, they've told us what they think ... so we followed up with blood tests to be sure," Snyder said. While testing the panda cubs, the zoo also tested an older female panda, Po, who is now 3 and previously thought to be a male. There are no plans to rename the cubs.
"Those names were fine for either sex. Actually they were slightly more appropriate for female cubs, so we're fine," said Snyder.
Despite the gender confusion, the cubs are doing well and have just learned to climb. Mei Lun and Mei Huan are the only twin giant pandas in the United States.
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